The concept of an “electronic nose” has been an active area of research for some decades. Researchers have been trying to provide such a device by attempting to couple an array of chemical odor sensors with a pattern-recognition system. Considerable interest has been generated by the Department of Homeland Security about the use of electronic devices in detecting volatile compounds to prevent explosive, chemical, or biological attacks.
Previous attempts at making electronic noses generally follow the same principle, coupling an array of chemical detectors with pattern recognition systems. However, they differ with respect to the selection of sensors. Common sensor designs include mass transducing, such as quartz microbalance, surface acoustic wave transducers, chemoresistors, and hybrids of such. In any event, it is greatly desired that sensors used for electronic noses and molecular detection exist and function on a very compact—even molecular—scale and exhibit very good electronic properties.
Nose-like sensing schemes derive their organizational principle from biological olfactory systems, where a large number (100 s) of sensor types are deployed with broad and overlapping sensitivities to an even larger number of volatile analytes. Reduced graphene oxide, or “chemically derived graphene”, has also shown potential as a vapor sensor material where residual oxygen defects (e.g. carboxylic acids or epoxides) provide binding sites for analyte molecules.
Graphene is a single-atom thick, two-dimensional material that has attracted attention because of its unique electronic, mechanical, and thermal properties. Because of these characteristics, graphene is useful in a range of electronic devices—such as sensors—and there is a corresponding interest in methods of producing graphenic materials.
Graphene has been actively studied as a chemical sensor since shortly after it was isolated in 2004. Increasingly sophisticated device processing has revealed that early measurements of graphene chemical sensing responses were amplified by unintentional functionalization.
Graphene is a true two dimensional material with exceptional electronic properties and enormous potential for practical applications. Graphene's promise as a chemical sensor material has been noted, but there has been relatively little work on practical chemical sensing using graphene, and in particular, how chemical functionalization may be used to sensitize graphene to chemical vapors.
Thus, there is a need for improving the ability of graphene to work as a chemical sensor. The invention is directed to these and other important needs.